The invention relates to an airbag module.
The airbags used in known airbag modules have in the non-inflated state a circular, round, elliptical or similar shape. Passenger airbags use airbags which are generally three-dimensional structures comprised of several parts joined together. They are arranged so that in the fully inflated state they fill out the space between the dashboard and the occupant. During inflation, more particularly before reaching the final shape, these airbags have a substantially spherical shape. These known airbags expand in the event of a crash extensively both in the direction of the occupant and upwards so that a sufficiently large protective cushion is provided for the occupant.
The known airbags have, however, the disadvantage that they have, as a result of the even expansion in the inflated state, areas which are not necessary for the protection of the driver but which have to be inflated as well as those areas necessarily inflated for the protection of the driver in order to ensure the protective function of the airbag as a whole.
Furthermore there is the disadvantage that the airbag, more particularly in the case of an module for the passenger, cannot be effectively inflated and unfolded without additional measures. Moreover the windscreen has to undertake important support and directing functions during inflation of the airbag. The windscreen cannot however fulfil these functions if it is destroyed, for example in the case of a secondary impact.
In order to overcome this disadvantage, it is already known to arrange arrester straps in the airbag which define the expansion of the airbag in the direction of the windscreen. Arrester straps are however additional parts which increases the costs of the airbag.
From JP-A- 092746 (Patent Abstract) an airbag is known for a passenger seat which has a cross-section which is restricted in the middle. Airbag material is thereby saved. The drawback with this airbag is that it is supported on the front windscreen of the motor vehicle. This supporting function can however no longer be fulfilled if the windscreen is destroyed. A further disadvantage is that the restricted cross-section is located at a point where the force introduction through the moving occupant at impact is greatest, therefore this airbag provides only a restricted restraint action.
Furthermore from EP A 0 590 845 a side airbag is known which has a restriction in the area of the inflation mouth of the airbag. It is thereby divided into a lower and an upper area which are adapted in size to the provisions of the door. The restriction serves to supply the gas to the lower and upper areas and has no protective function. Since the lower and upper areas are inflated suddenly from area of the restriction, the seams and fabric are heavily stressed.